~Update the windows app template and migration to use `CMP0135` when
cmake version is >= 3.24.~

Update app templates' and examples' CMakeLists.txt to use
`cmake_policy(VERSION`. https://github.com/flutter/packages/pull/3828
should obviate the need for a migration.

Addresses https://github.com/flutter/flutter/issues/116866

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* Add Windows unit tests to plugin template

Adds an example native unit test to the plugin template for Windows,
matching the format we use for our 1P plugin example app unit tests.
Once these have been added for all platforms+languages, they will be
documented on a new plugin development page to explain their use.

Since we don't appear to be running our current plugin e2e tests for
Windows, this adds a new configuration to run them. I haven't
`led`-tested this, so it may not work, but this will give a starting
point for getting them running.

Part of https://github.com/flutter/flutter/issues/82458

* Minor fix

* Add test owner

* Fix typo

* Fix test feature flag

When we landed the CMake minimum requirement constraint for Visual
Studio 2019, we landed it with minimum version 3.15, since that's what
was shipping with the current version of VS 2019 at the time. Looking at
the release notes of earlier versions, it's clear that earlier versions
of Visual Studio 2019 shipped with version 3.14. See:
https://devblogs.microsoft.com/cppblog/visual-studio-cmake-support-clang-llvm-cmake-3-14-vcpkg-and-performance-improvements/

Looking at release notes for CMake 3.15, there are no features/fixes
introduced in that version that we are dependent on.
https://cmake.org/cmake/help/latest/release/3.15.html

Issue: https://github.com/flutter/flutter/issues/88589

* First pass at CMake files; untested

* First pass of adding CMake generation logic on Windows

* Misc fixes

* Get bundling working, start incoprorating CMake build into tool

* Fix debug, exe name.

* Add resources

* Move cmake.dart

* Rip out all the vcxproj/solution plumbing

* Fix plugin cmake generation

* Build with cmake rather than calling VS directly

* Adjust Windows plugin template to match standard header directory structure

* Pass config selection when building

* Partially fix multi-config handling

* Rev template version

* Share the CMake generation instead of splitting it out

* VS build/run cycle works, with slightly awkward requirement to always build all

* Update manifest

* Plugin template fixes

* Minor adjustments

* Build install as part of build command, instead of separately

* Test cleanup

* Update Linux test for adjusted generated CMake approach

* Plugin test typo fix

* Add missing stub file for project test

* Add a constant for VS generator